Rotary impact tool



March 26, 1957 E. G. ROGGENB URK 2,786,376

I ROTARY IMPACT TOOL Filed Jan. 18 1954 3 Sheets- Sheet 1 Ill F'IG. I

A ORNEY March 1957 E. G. R-OGGENBURK 2,786,376

ROTARY IMPACT TOOL Filed Jan. 18, 1954 3 Sheets-Shpet 2 INVENTOR. EARLG. ROGGENBURK BY 7747i A ORNEY March 26, 1957 E. G. ROGGENBURK 2,786,376

ROTARY IMPACT TOOL F'iied Jan. 18. 1954 s Shets-Sheet s 6O 37 so 3OINVENTOR.

RNEY

ROTARY IMPACT TOOL Earl G. Roggenburk, Cleveland, Ohio ApplicationJanuary 18, 1954, Serial No. 404,747

15 Claims. (Cl. 81-52.3)

lThiS invention pertains to impact tools and, more particularly, to anew and improved mechanism for controlling the impact action of thetool.

It is an object of this invention to provide an impact tool, such as awrench, screw driver or the like, which has a new, improved and lessexpensive impacting mechanism.

A further object of the invention is to provide an impact tool which hasa minimum of parts, moving and stationary.

A further object of this invention .is to provide an impact tool whichhas improved impacting action.

Still another object of this invention is to provide an impact toolwhich can easily be manufactured and assembled.

It is also an object of the invention to provide an impact tool whoseimpacting parts can quickly, easily and inexpensively be replaced afterthey have become worn.

A further object of the invention is to provide an impact tool whoseimpacting parts have a long useful life under severe impact loads.

Still another object of this invention is to provide an impactcontrolling mechanism with means assuring that the impact occurs at atime when it will result in the maximum torque being applied to thepiece being driven.

For a better understanding of the present invention together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings and itsscope will be pointed out in the appended claims.

In the drawings:

Fig. 1 is a side view, partially broken away, showing this inventionapplied to a pneumatic driving motor.

Fig. 2 is a sectional view taken along line 22 of Fig. 1, showing theimpacting mechanism.

Fig. 3 is a sectional view taken along line 3-3 of Fig. 2.

Fig. 4 is a sectional view showing a modified form of the invention.

This invention is particularly applicable to impact tools driven bycompressed fluid, such as air, and is particularly suitable for impactwrenches, screw drivers and the like.

Because the invention has been perfected for use with an air-drivenimpact wrench, it will be described in such connection.

As shown in Fig. l a housing 19 encloses an air-driven motor, thedetails of which are shown, described and claimed in my applicationSerial Number 309,980, filed September 17, 1952, for a Rotary FluidMotor. However, it is to be understood that other fluid-driven motorsmay be used.

The rotary driving motor within the housing 19 drives a splined outputshaft 20 which is coupled into a splined socket 21 in a massive hammermeans indicated generally by the reference character 22.

The massive hammer means 22 'is mounted within the housing for coaxialrotation with the driving motor, and comprises a first section 25 ofrelatively large diameter nited State Pawn: or

A 2,786,376 Patented Mar. 26, 1957 and a second section 26 of relativelysmaller diameter. The splined socket 21 is located in the hammer section25 of large diameter, and the section 26 of smaller diameter has a roundbore 27 whose axis is in a direction perpendicular to the direction ofthe axis of rotation of the hammer means and driving motor. Within thebore 27, and forming part of the massive hammer means, is a hammer .pin28 which can slide in and out with respect to the massive sections 25and 26. The mass of the ham mer pin 28 is eccentric with respect to theaxis of rotation of the tool so that as the driving motor rotates themassive hammer means centrifugal force tends to throw the hammer pin 28out of the bore 27. Means are provided within the bore 27 and back ofthe hammer pin 28 to prevent the hammer pin from moving too far out ofthe bore 27. The means shown in Figs. 1 and 2 comprise spring means 29,and the means shown in Fig. 4 comprises partial vacuum, as will beexplained in more detail. One end of the spring 29 is connected to across-pin 30 inserted in a bore 31 extending across the bore 27. Theother end of the spring 29 is connected to the pin 32 which is connectedacross the hammer pin 28. As shown in Fig. 3 the inside end 33 of thehammer pin 28 is cup-shaped providing an annular flange 34 across whichthe pin 32 is secured and into which one end of the spring 29 extends. Asecond spring 35 is mounted in the bore 27 between the cross-pin 30 andthe end surfaces of the annular flange 34 on the hammer pin 28. Themassive hammer means also includes a support shaft 36 integral with thesecond massive section 26. The hammer pin 28 preferably is round and ithas a groove 37 into which the end of a limit pin 38 extends. The limitpin 38 is mounted through the massive section 26 into the bore 27. Whenthe hammer pin 28 is thrown outwardly by centrifugal force the limit pin38 stops the outward movement of the hammer pin before it goes too far.The hammer pin 28 is provided with a flat face 39 where it forcefullyengages an anvil. It also prevents the hammer pin 28 from rotating inthe bore 27. Thus the massive hammer means 22 comprises the first andsecond massive sections 25, 26, the hammer pin 28 and its associatedpins 31, 32, 38, springs 29, 35, and the support shaft 36.

The output drive means comprises a drive shaft 45 having a bore 46within which the support shaft 36 extends with a close running fitwhereby the shaft 36 may easily turn with respect to the drive shaft 45.The drive shaft 45 has means at its outer end 47 to connect to devicesfor running nuts, bolts, screws, etc., and at its other end is providedwith an anvil portion 48 which extends over the massive section 26 ofthe hammer means. Thus the anvil 48 is located in the circumferentialpath occupied by the portion of the hammer pin 28 which extends outsideof the bore 27 when the hammer means is rotating. This causes the hammerpin 28 to strike the anvil 48 a. hard blow which is translated to theoutput shaft 45 in the form of a torsional force of high instantaneousvalue.

In order that the impact tool operate at its highest efliciency, it isnecessary that the output shaft 45 be tightly coupled to whatever isbeing driven, for if it is not closely coupled to the nut or bolt anappreciable amount of the impact force is absorbed by the mass of theoutput shaft 45. In other words, if the force transmission path from theanvil 48 to the nut being tightened is not closely coupled, much of theimpact force from the hammer is wasted in accelerating the output shaft45. This force is then unavailable to do useful work. In order to makesure that the impact tool of this invention operates at maximumefiiciency for every blow the end face 50 of the anvil 48 is inclined atan angle other than degrees with respect to the axis of rotation of theanvil. The hammer means 22 is provided with a bore 51 in the firstmassive section 25 of the hammer means at a lbcatio'n spaced from therotary path of the inclined face 50' of the" advil 48. The axis of thesore 51 is preferably parallel to the axis of rotation of the harnmermeans. A positioning pin 52 is mounted in the bore 51 with a portion 53protruding out to a. location where, upon rotation of the hammer means,it will engage the inclined face 50 of the anvil. A spring 54 is mountedin the bore 51 and a screw plug 55 or the like closes the end of thebore. The spring 54 urges the positioning pin 52 forward towardengagement with the inclined face 50 of the anvil. As the hammer meansrotates under force from the driving motor the positioning pin engagesthe inclined face 50 of the anvil 48 thereby rotating the anvil, theoutput shaft 45 and any nut or bolt holding devices until the forcetransmission path is closely coupled, then the hammer pin 28 hits theedge 56 of the anvil and delivers a forceful blow to' the nut or bolt.

After the hammer hits its blow, its rotary motion is stopped and thereis zero centrifugal force on the hammer pin 28. The spring 29 which wasextended as the hammer pin moved part way out of the bore 27 undercentrifugal force then pulls the hammer pin back into the bore 27,causing it to clear the underneath surface 57 of the anvil and allowingthe motor once again to spin the hammer means 22 at a rate sufficientthat the centrifugal force on the hammer pin overcomes the oppositeforce of the spring 29. When the spring 29 pulls the hammer pin backintothe bore 27 it does so with considerable fo'r'ce'. Therefore it ishighly desirable to provide a shock-absorbing compression spring 35against which the annular flange 34 of the hammer pin hits. Thisprevents distortion of spring 29.

As shown in Fig. 1, for forward running of the tool the apex 60 of theface 50 of the anvil should be in engagement with the pin 52 at theinstant the hammer pin 28 strikes the anvil face 56. For reverseoperation the mechanism should be so positioned that it engages the apex60 at the instant the hammer pin 28 strikes the reverse face 58 of theanvil.

In the embodiment shown in Fig. 4 parts similar to the parts shown inFigs. 1-3 carry the same reference characters. in this embodiment thehammer pin 28 is machined to have a close sliding fit with respect tothe bore in the section 26 of the hammer means 22, and an annular O ring79 is located between the hammer section 26 and the hammer pin 28 inorder to provide a substantially air-tight space 71 at the base of thehammer pin 28. A screw plugJ71 is provided in the section 26 at the baseof the hammer pin 28.

Under the influence of high centrifugal force the hammer pin 23 extendsout of the bore 27 and strikes a blow against the anvil face 56. Apartial vacuum is created in the substantially air-tight space 71 whenthe hammer pin 23 flies out, and this partial vacuum pulls the pin backinto the bore 27 after the impact blow has been struck and the hammerhas substantially ceased to rotate. The hammer pin 28 will not be pulledback into the bore 2'7 with sufiicient force to cause damage since thereis always a slight amount of air in the space 71 which acts as an aircushion as the pin is pulled back into the bore 27.

In the event there should be a slight leak around the O ring 7% and toomuch air is obtained in the air space 7i,-the operator should remove theair-tight screw plug '72, then position the hammer pin 28 in the properposition'in the bore 27 to provide the correct size air space 71, thentighten the screw plug '72. This quickly and easily re-establishes thecorrect amount of air in space 71 to permit the hammer pin 23 to fly outunder the right amount of centrifugal force, and to provide the propercushioning action when the hammer pin slams back into the bore 27.

While there have been described what are atpresent considered to hemepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that .4 various changes and modifications may be madetherein without departing frbifi the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is:

1. In a rotary impact tool having a rotary driving motor; massive rotaryhammer means mounted for coaxial rotation with and driven by said rotarymotor; said hammer means having a sealed bore whose axis isperpendicular to the axis of rotation of said hammer means, a hammer pinslidably mounted within said here and eccentric with respect to saidaxis of rotation of said hammer means whereby rotary motion-of saidhammer means establishes a centrifugal force which is the sole forcemoving said hammer pin partially out of said bore, means within saidbore exerting a force on said hammer pin opposite to said centrifugalforce; and output drive means mounted for coaxial rotation with saidhammer means and including an anvil portion located in thecircumferential path occupied by the said portion of said hammer pinoutside of said bore when rotating, whereby said hammer pin strikes saidanvil when centrifugal force causes said hammer pin to project out ofsaid bore.

2. A rotary impact tool as set forth in claim 1, further characterizedby tension spring means within said bore connected to said hammer pin toexert a force on said hammer pin in opposition to centrifugal force.

3. In a rotary impact tool having a rotary driving motor; massive rotaryhammer means mounted for coaxial rotation with and driven by said rotarymotor; said hammer means having a bore whose axis is perpendicular tothe axis of rotation of said hammer means, a hammer pin slidably mountedwithin said bore and eccentric with respect to said axis of rotation ofsaid hammer means whereby rotary motion of said hammer means tends tothrow said hammer pin partially out of said bore, retracting meanswithin said bore exerting a force on said hammer pin opposite to saidcentrifugal force, shock absorbing spring means within said bore forengaging said hammer pin as said hammer pin is retracted within saidbore by said retracting means upon sudden reduction in centrifugal forcewhen said hammer pin strikes said anvil.

4. A rotary impact tool as set forth in claim 1, further characterizedby said bore and the back end of said hammer pin establishing asubstantially air-tight compartment within which a partial vacuum isestablished as said hammer pin moves due to centrifugal force, saidpartial vacuum exerting a force on said hammer pin opposite to saidcentrifugal force for returning said hammer pin within said bore afterthe hammer pin strikes the anvil.

5. A rotary impact tool as set forth in claim 1, further characterizedby said anvil portion having an end face inclined at an angle other thandegrees with respect to the axis of rotation of said anvil means, andcharacterized by said hammer means including a circumferential portionopposite and spaced from the rotary path of said inclined face on theanvil means, a bore whose axis is substantially parallel to the axis ofrotation of said hammer means located in said portion of the hammermeans spaced opposite said inclined face, a positioning pin slidablymounted in said bore, and means in said bore biasing said positioningpin into engagement with said inclined face.

6. A rotary impact tool as set forth in claim 5, further characterizedby the location of said positioning pin in said hammer means being sorelated to the position of said hammer pin that said positioning pinengages the inclined face of said anvil means and rotates said anvilmeans to take up all play between the anvil and a tool to which itimparts rotational force prior to said hammer pin striking the saidanvil.

7. In a rotary impact tool having a rotary driving motor; massive rotaryhammer means mounted for coaxial rotation with and driven by said rotarymotor; said hammer means having a sealed bore whose axis isperpendicular to the axis of rotation of said hammer means; a hammer pinslidably mounted within said bore and eccentric with respect to saidaxis of rotation of said hammer means whereby rotary motion of saidhammer means establishes a centrifugal force which is the sole forcemoving said hammer pin out of said bore, means preventing said hammerpin from being thrown completely out of said bore, means within saidbore in en gagement with said hammer pin for establishing a force onsaid hammer pin opposite to said centrifugal force when the hammer pinis partially out of said bore, and output drive means mounted forcoaxial rotation with said hammer means and including an anvil portionlocated in the circumferential path occupied by the said portion of saidhammer pin outside of said bore when rotating, whereby said hammer pinstrikes said anvil when centrifugal force causes said hammer pin toproject out of said bore.

8. A rotary impact tool as set forth in claim 7, further characterizedby tension spring means Within said bore one end of which is connectedto said hammer pin and the other end of which is secured to a fixedportion of said hammer means with respect to which said hammer pin movesdue to centrifugal force.

9. A rotary impact tool as set forth in claim 8, further characterizedby compression spring means Within said bore located between the end ofthe hammer pin within said bore and the said fixed portion of saidhammer means.

10. A rotary impact tool as set forth in claim 9, further characterizedby the end of said hammer pin within said bore being cup shaped, a pinconnected across the walls of said cup portion, one end of said tensionspring being connected to said pin, the lip of said cup portion engagingsaid compression spring.

11. In a cyclically operating rotary impact tool having a rotary drivingmotor; massive rotary hammer means mounted for coaxial rotation with anddriven by said rotary motor; said hammer means having a bore closed atits bottom end throughout the entire operating cycle and whose axis isperpendicular to the axis of rotation of said hammer means, a hammer pinslidably mounted in sealing engagement within said bore and eccentricwith respect to said axis of rotation of said hammer means wherebyrotary motion of said hammer means tends to throw said hammer pin out ofsaid bore establishing a partial vacuum in the bottom of said bore whichexerts a force on said hammer pin opposite to said centrifugal force;and output drive means mounted for coaxial rotation with said hammermeans and including an anvil portion located in the circumferential pathoccupied by the said portion of said hammer pin outside of said borewhen rotating, whereby said hammer pin strikes said anvil whencentrifugal force causes said hammer pin to project out of said bore.

12. A rotary impact tool as set forth in claim 11, further characterizedby an O-ring around the portion of said impact pin always within saidbore for establishing a seal between the wall of the bore and the wallof the impact pin.

13. An impact tool as set forth in claim 11, further characterized by aremovable air-tight plug located in the wall of said bore forestablishing upon removal a communication between atmosphere and thesaid bore.

14. In a rotary impact tool having a rotary driving motor; massiverotary hammer means mounted for coaxial rotation with and driven by saidrotary motor; said hammer means having a bore Whose axis isperpendicular to the axis of rotation of said hammer means, a hammer pinslidably mounted within said bore and eccentric with respect to saidaxis of rotation of said hammer means whereby rotary motion of saidhammer means throws said hammer pin partially out of said bore, meansexerting a force on said hammer pin opposite to said centrifugal force,output drive means mounted for coaxial rotation With said hammer meansand including an anvil portion located in the circumferential pathoccupied by the said portion of said hammer pin outside of said borewhen rotating and including an end face portion inclined at an angleother than degrees with respect to the axis of rotation of said anvilmeans, said hammer means having a portion opposite and spaced from therotary path of said inclined face on the anvil means, said hammer meanshaving a bore whose axis is substantially parallel to the axis ofrotation of said hammer means and located opposite said inclined face, apositioning pin slidably mounted in said bore, and means in said borebiasing said positioning pin into engagement with said inclined face.

15. In a rotary impact tool having a rotary driving motor; massiverotary hammer means mounted for coaxial rotation with and driven by saidrotary motor and including a hammer pin, means causing an impact portionof said hammer pin to extend out into an annular impact path duringrotation of said hammer means, output drive means mounted for coaxialrotation with said hammer means and including an anvil portion locatedin said annular impact path occupied by the said impact portion of saidhammer pin and including an end face portion inclined at an angle otherthan 90 degrees with respect to the axis of rotation of said anvil meansfacing said hammer means, said hammer means having a portion oppositeand spaced from the rotary path of said inclined face, said hammer meanshaving a bore whose axis is substantially parallel to the axis ofrotation of said hammer means and located opposite said inclined face, apositioning pin slidably mounted in said bore, and means in said borebiasing said positioning pin into engagement with said inclined face.

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